Apply some triple antibiotic cream with pain reliever (one brand is Neosporin Plus) and a large, soft bandage--one of the type that is non-stick. Try to apply the bandage so that it doesn't break the blister. A blister is a sort of natural bandage itself. If you leave it alone (other than the cream and bandage) it will heal better. Also, be sure to get Neosporin cream, not ointment.